Command line

As soon as you have logged in via SSH or directly on the industrial PC with keyboard and monitor, the command line is available to you. After logging in, a welcome message is displayed first, followed by the command prompt where you can enter commands.

Linux BTN-000tr8p8 6.17.7-rt5-bhf1-248071-3abacfd8c4f8 #1 SMP PREEMPT_RT Tue Nov 4 11:35:53 UTC 2025 aarch64

The programs included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Mon Jan 26 14:13:55 2026 from fe80::a39f:a0d2:f0b4:5280%end0
Administrator@BTN-000tr8p8:~$

The Shell

The command prompt is provided by a program called Shell. The shell is a command line interpreter that allows you to interact with the operating system by typing commands. The standard shell on most Linux® systems is called bash (Bourne Again Shell). However, there are also other shells such as zsh, fish or tcsh, which are also available and can be installed.

Commands in the command line

Commands are usually structured as follows:

command [options] [arguments]

• command is usually the name of a program or Toolbox that you want to run.
• options are usually preceded by a hyphen - or double hyphen -- and change the behavior of the command.
• arguments are the targets or inputs to which the command refers.

Most programs offer help that provides information on how to use the command. This is usually accessed via -h or --help.

For example, to get help on the ping command, you can execute the following command:

ping -h

The output looks as follows:

Usage
   ping [options] <destination>

Options:
   <destination>      DNS name or IP address
   -3                 RTT precision (do not round up the result time)
   -a                 use audible ping
   -A                 use adaptive ping
   -B                 sticky source address
   -c                 <count> stop after <count> replies
   -C                 call connect() syscall on socket creation

--- snipped ---

For more details see ping(8).

Manpages

You can use the command man to display the manpages of a command. For example, to display the manpages for the command ping, execute the following command:

man ping

The output looks as follows:

NAME
       ping - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS

       ping [-aAbBdCDfhHLnOqrRUvV346] [-c count] [-e identifier]         [-F flowlabel] [-i interval] [-I interface]
       [-l preload] [-m mark] [-M pmtudisc_option] [-N nodeinfo_option] [-w deadline] [-W timeout] [-p pattern]
       [-Q tos] [-s packetsize] [-S sndbuf] [-t ttl] [-T timestamp option] [hop...] {destination}

DESCRIPTION
       ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams ("pings") have an IP and ICMP header, followed by a struct timeval and then an arbitrary number of "pad" bytes used to fill out the packet.

       ping works with both IPv4 and IPv6. Using only one of them explicitly can be enforced by specifying -4 or -6.

       ping can also send IPv6 Node Information Queries (RFC4620). Intermediate hops may not be allowed, because IPv6 source routing was deprecated (RFC5095).

OPTIONS
       -3
       RTT precision (do not round up the result time).

       -4
       Use IPv4 only.

--- snipped ---

You can exit the manpage display with q.

The manpages are always structured in the same way for all commands so that the information can be found quickly. Outside the command line, the manpages for each command can be called up at the following web pages: https: //manpages.debian.org/<command> and viewed in the web browser.

Users and groups

Under Linux®, each process runs under a specific user account. User accounts are used to manage authorizations and access control for files and system resources. Each user account belongs to one or more groups; groups make it easier to manage rights for several users at the same time. You can use the command id to display information about the current user and their groups:

Try out the following commands:

id

You can use sudo to execute a command with elevated rights (e.g. as root). To check the identity of the user using sudo, execute the following command, for example:

sudo id